1. Field of the Invention
The present invention relates to a lens cap for an optical module, an optical module, and a method for manufacturing a lens cap for an optical module.
2. Background Art
Lens caps for an optical module using a conventional press lens use a material such as SUS430 or SF-20T having a coefficient of linear expansion of 10 ppm/K or more for a metal barrel (e.g., see paragraph 0014 of Japanese Patent Laid-Open No. 2009-37055). That is, a material having a greater coefficient of linear expansion than the coefficient of linear expansion of 6 to 8 ppm/K of glass is used for the barrel. This difference in the coefficient of linear expansion between the lens glass and the metal barrel causes the metal barrel to tighten the lens in a cooling process after molding of a lens at 600 to 800° C. Thus, it is possible to improve airtightness between the lens and the metal barrel.